In the processing of color film or prints the maintenance of developer activity is necessary for uniform development. In recent years, it has become the practice to introduce a replenishing solution to the developing solution in order to replace depleted chemicals of the processing solution and the solution carried away. Unless this is done there will be a build-up of reaction by-products formed as development progresses. Also, the concentration of reaction by-products may in time exceed the concentration of developing agent. As the reaction by-products increase the probability of the developer agent being absorbed by the silver halide grain decreases, and the likelihood of uneven development increases. Hence, replenishment requires restoration of developing agents, preservatives and usually alkali, since their concentrations fall during the developing process.
A wide range of photographic replenishers are known in both ready-to-use solutions and compounded forms. The compounded forms include liquid concentrates, which have only to be diluted with water to obtain a working strength solution, and powder types which have to be dissolved in solution. Both the ready-to-use and compounded forms present some individual problems ranging from difficulty of uniform mixing of components in the compounded forms to the high cost of shipping the extra weight of water volume in a ready-to-use solution.
The ready-to-use replenishing solutions are convenient for the user, but their large size makes shipping more expensive, and the containers take up valuable storage space. To overcome these disadvantages, there has been a trend to reduce the size of the packaging, and thus, subsequently providing a savings on shipping costs. One way to achieve this goal is to make either an all-powder or a liquid concentrate replenishing composition.
Typically, powder mixes are dissolved and brought to working strength with the addition of water. However, powdered replenishing compositions can be difficult to dissolve, especially if caking of the powder components occurs. Furthermore, powder mixes contain many substances which react with each other by an oxidation-reduction reaction necessitating the packaging of the components separately. The mixing of the components must be deferred until the time a working solution is actually used.
Liquid concentrates are an alternative to the powder mixes, but the increased water volume makes them more expensive to ship, handle and store than the powder mixes. While a higher degree of concentration will reduce some of the volume of liquid it also presents several additional problems. Because of the high dilution required to obtain working strength solutions, the concentrates usually contain maximum levels of photographic processing ingredients. However, because most developing agents are less soluble in a solution with a high pH than in a solution with a neutral pH it can be difficult to increase the concentration of the included developing agent without compounds coming out of solution.
It is no less significant that with concentrated liquid replenishers there is a marked deterioration of developing agents. This is due to a number of reasons including: high alkalinity of most replenishing solutions, decomposition of sulfites in the replenishing composition to sulfur dioxide with the subsequent degradation of the developing agent and possible hydrolysis of the oxidation product of some developing agents. Heretofore, to overcome the forgoing problems, replenishers have been packaged and shipped as multi-part liquid systems, packaging incompatible ingredients into separate containers to protect the developing agent, for example, from deterioration. The separate parts are mixed together immediately prior to being used. Of course, this method may protect the developing agents, but also raises the level of possible mishaps in the preparation regime, lack of convenience, additional needs for storage space and increased shipping costs.
Accordingly, there is a need for improved one-part liquid concentrated replenishers which can be shipped economically, require minimal storage space, eliminate the need for mixing several different components, provide for high concentrations of developing agents, and prevent deterioration of developing agents in the concentrate.